When Sen. Barack Obama came to Portland in May, 72,000 people turned up to greet him.

Now, the Obama campaign is returning the favor. Nancy Floyd, the Portland-based founder and managing director of energy technology investment firm Nth Power, has been invited to speak during prime time on Tuesday night at the Democratic National Convention in Denver, Colo.

Floyd is scheduled to speak between 6 and 6:30 p.m. Pacific time, just before former Virginia Gov. Mark Warner, who’s running for the U.S. Senate this year.

On Friday last week, just 20 minutes after receiving her invitation by phone, Floyd, a dynamic, petite woman, was jumping up and down.

“It’s a wonderful opportunity to provide, in prime time, a business person’s perspective on the economic aspect of clean energy,” she said this week, speaking in calmer and more measured cadences.

“Clean technology shouldn’t be a political issue,” said Floyd. “It’s a jobs issue, and a U.S. competitiveness issue.”

Floyd has been involved with alternative energy technologies since she founded one of the first wind development firms in the country, in 1982. Floyd sold NFC Energy Corp. three years later, generating a 25-fold return on invested capital.

Nth Power began investing in energy technologies in 1997. The firm now manages $420 million in invested capital.

Among its investments are Oregon companies Serveron Corp., which developed technology for electric utility networks, and Thetus Corp., which is developing semantic search technology that’s getting attention from energy utilities, refineries and alternative-energy producers.

Floyd’s appearance at a historic nominating convention — Sen. Obama would be the nation’s first African-American president, if he wins — could boost visibility for Oregon’s new and fast-growing alternative energy industry.

While Floyd wants to address the big picture, she’s planning to slip in a strategic reference to Oregon.

“I’m going to point out that the most courageous entrepreneurs, the best minds in the country, from the Silicon Forest of Oregon to Route 28 outside of Boston and points in between, are now working on addressing clean energy technology,” she said.